USB: legousbtower: make poll notice disconnect

poll needs to return an error if a device is disconnected
  - make poll check for device's presence
  - wake all waiters in disconnect

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 97efeaec4d52..faa6d623de78 100644
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -552,6 +552,9 @@ static unsigned int tower_poll (struct file *file, poll_table *wait)
 
         dev = file->private_data;
 
+        if (!dev->udev)
+                return POLLERR | POLLHUP;
+
         poll_wait(file, &dev->read_wait, wait);
         poll_wait(file, &dev->write_wait, wait);
 
@@ -1025,6 +1028,9 @@ static void tower_disconnect (struct usb_interface *interface)
                 tower_delete (dev);
         } else {
                 dev->udev = NULL;
+                /* wake up pollers */
+                wake_up_interruptible_all(&dev->read_wait);
+                wake_up_interruptible_all(&dev->write_wait);
                 mutex_unlock(&dev->lock);
         }